Chaetonotus (Chaetonotus) similis Zelinka, 1889

Kånneby, Tobias, 2013, New species and records of freshwater Chaetonotus (Gastrotricha: Chaetonotidae) from Sweden, Zootaxa 3701 (5), pp. 551-588 : 566-567

Chaetonotus (Chaetonotus) similis Zelinka, 1889

( Fig. 10 )

Localities: Artificial pond, Nybro, Småland (N 56º 44’ 89’’; E 15º 54’ 27’’) June 28, 2008; Gravel pit, Åhus, Skåne (N 55º 55’ 43’’; E 14º 15’ 08’’), April 10, 2009; Sphagnum spp. bog at highway E10, Lapland (N 68º 26’ 04’’; E 18º 14’ 53’’), July 1, 2010; Lake with grass at highway E10, Lapland (N 68º 20’ 915’’; E 19º 02’ 210’’), July 6, 2010.

Material: 4 specimens.

TL, 198–221 µm; FL, 23–28 µm; AL, 15–16 µm; PhL, 58–63 µm; MD, 7–9 µm; CW, 13–17 µm; TNC, ~18; DC, 11–13; DR, 25–27; VLC, 7–8; HS, 2– 3 x 3–4 µm; NS, 4 x 3–4 µm; DS, 7– 9 x 6–8 µm; HSp, 4–10 µm; NSp, 5–10 µm; DSp, 15–25 µm; VC, 7–9; VTS, 13– 17 x 6–8 µm.

Head clearly five-lobed with two pairs of cephalic sensory ciliary tufts. Cephalion and pleurae well developed. Hypostomium developed as a plate with two teeth. Two pairs of sensory bristles, posterior pair emerging from subtriangular double keeled scales at U78. Furca straight with adhesive tubes constituting approximately 2/3 of the total furca length. Dorsal surface covered by three-lobed to crescent-shaped scales with slightly curved barbed spines. Scales and spines increase in size towards the posterior end. Dorsally an area anterior to the caudal incision with smaller scales with short simple spines, as in C. (C.) maximus . Laterally at the posterior dorsal end and at the caudal incision 5 longer and stouter spines.

Ventrolateral scales and spines similar to those of the dorsal surface, but they decrease in size towards the ciliary bands. Ventral interciliary area covered by oval keeled scales with short simple spines. A pair of large oval keeled terminal scales with a simple spine, up to 10 µm in length.

Mouth terminal. Pharynx with weak posterior swelling. PhIJ at U32–33. Intestine straight with anus at U84– 86.

According to Kisielewski (1981) C. (C.) similis is a very variable species, especially when it comes to size and length of spines. The Swedish specimens, all in parthenogenetic phase, generally fall within the limits of literature data. The number of dorsal columns is below (11–13) the values (14–17) reported in the literature.

Previously reported from Austria (Zelinka 1889), Great Britain (Martin 1981), Hungary (Valkanov 1937), Italy (Marcolongo 1910), Poland (Kisielewski 1986), Romania (Rudescu 1967), Russia (Preobrajenskaja 1926), Spain (Real 1940), Sweden (Kånneby et al. 2013), Brazil (Kisielewski 1991) Canada (Schwank 1990), India (Naidu & Rao 2004), Israel (Kisielewski 1999), Japan (Saito, 1937), Paraguay (Daday, 1905) and USA (Zelinka 1889).

Figures

FIGURE 10. Chaetonotus (C.) similis. A) Habitus. B) Dorsal view of posterior trunk region showing distribution of scales and spines. Scale bars: A, 25 µm; B, 10 µm.